bloom filter hashing

hashk.js

djb2b = function (str, seed) {
    var i, l = str.length, hash = seed || 5381;
    for (i = 0; i < l; i++) {
        hash += (hash << 5) + (str.charCodeAt(i)|0);
        hash = hash & hash; // 32bit cast
    }
    return hash;
}

sdbm = function(str, seed){
    var hash = seed || 0;
    for (i = 0; i < str.length; i++) {
        char = str.charCodeAt(i);
        hash = char + (hash << 6) + (hash << 16) - hash;
        hash = hash & hash; // 32bit cast
    }
    return hash;
}

// http://citeseer.ist.psu.edu/viewdoc/download?doi=10.1.1.152.579&rep=rep1&type=pdf
hashk = function (k, v, modulo) {
    var a = djb2(v), b = sdbm(v), hashes = [];
    for (var i=1, hash; i<=k; i++) {
        hash = a + b * k;
        hashes.push(
            modulo ? Math.abs(hash) % modulo : hash
        );
    }
    return hashes;
}